The present invention is directed to an apparatus for processing a microelectronic workpiece. More particularly, the present invention is directed to an improved input/output station that receives multiple microelectronic workpiece cassettes and selectively aligns the cassettes with and transfers them to a workpiece cassette staging assembly. For purposes of the present application, a microelectronic workpiece is defined to include a workpiece formed from a substrate upon which microelectronic circuits or components, data storage elements or layers, and/or micro-mechanical elements are formed.
Multiple processes must be executed upon a microelectronic workpiece to manufacture desired microelectronic circuits, devices, or components. These processes are generally executed in processing tools that are specifically designed to implement one or more of the requisite processes. In order to automate the processing and minimize operator handling, tool architectures have been developed that incorporate multiple processing stations and automated transfer of the microelectronic workpieces from one processing station to the next. For example, tools of this type are available from Semitool, Inc., of Kalispell, Mont., under the brand names Equinox(copyright), LT-210(copyright), LT-210C and Millennium.
In such tools, the workpieces are processed individually at the various processing stations. Furthermore, multiple workpieces are concurrently processed at different processing stations. Thus, one workpiece may be processed in one of the processing stations while another workpiece is concurrently processed in another one of the processing stations. In this way, a pipeline processing approach can be developed, which enhances production throughput. Additionally, processing steps that take longer to perform may have multiple processing stations devoted to performing that particular processing step, thereby enhancing production throughput.
In many instances, multiple microelectronic workpieces are concurrently supplied to the tool in a cassette. Each cassette generally includes a plurality of individual workpiece positions or slots, where each slot is adapted to hold an individual workpiece. Typically, a first cassette containing a plurality of workpieces is loaded into the tool, and a second empty cassette is loaded into the tool for receiving the same workpieces after they have been processed. Alternatively, the processed workpieces may be returned to their original cassette, thereby enabling concurrent loading of two cassettes containing unprocessed workpieces.
When processing of the workpieces contained within a given cassette is complete, an operator removes the one or more cassettes containing the processed workpieces and loads new cassettes that contain the next set of workpieces that are to be processed. Consequently, periodically an operator must remove processed workpieces from the tool and supply the next set of workpieces that are to be processed. As workpiece processing tools achieve greater workpiece throughput, the time it takes for the tool to process the workpieces contained within a cassette decreases. As a result, operators must more frequently load and unload the workpiece cassettes, requiring temporary interruption of any workpiece processing taking place at that time. Furthermore, during this loading and unloading time, the operator is prevented from attending to other duties requiring a higher level of skill. Consequently, to the extent that the time required for operator activity can be reduced or minimized overall microelectronic fabrication efficiencies can be enhanced. Moreover, because operators can be a source of particle contamination, less frequent operator interface with the tool can reduce the potential for particle contamination of the workpieces.
The present inventors have recognized that overall microelectronic fabrication efficiencies can be increased by reducing the frequency of loading/unloading cycles for a given number of workpieces. Further, they have recognized that one manner of reducing the frequency of loading/unloading cycles is to allow loading and/or unloading of a greater number of workpieces to and/or from the tool during a given cycle. This would enable the tool to process workpieces for a longer period of time before the next load/unload cycle requires operator activity. Still further, the present inventors have recognized the advantages of developing an apparatus and/or method that allows a greater number of workpieces to be loaded and/or unloaded from a tool while concurrently requiring minimal modifications and/or adjustments to an existing set of tools that are already installed and operational at a microfabrication facility and which occupies a minimum amount of manufacturing floor area.
To this end, the present inventors have developed a workpiece cassette inventory assembly that receives multiple workpiece cassettes and selectively aligns the cassettes for transfer to and from a staging assembly that allows access to the individual workpiece slots of the cassettes such as, for example, a lift/tilt assembly or the like.
An apparatus for providing access to individual workpiece positions in a microelectronic workpiece cassette is set forth. The assembly comprises a workpiece cassette inventory assembly including a plurality of inventory cassette supports for receiving a plurality of cassettes. The plurality of cassettes can be selectively indexed to provide one or more of the plurality of cassettes to a workpiece cassette staging assembly by adjusting the positional alignment of the plurality of cassettes. The workpiece cassette staging assembly includes one or more staging cassette supports for receiving the one or more indexed cassettes from the workpiece cassette inventory assembly and repositions the one or more indexed cassettes, so as to provide access to the one or more microelectronic workpieces contained within the indexed cassettes, wherein the inventory cassette supports of the indexed cassettes are positionally aligned with the corresponding staging cassette support. This allows a tool incorporating the assembly to process a larger number of microelectronic workpieces between user intervening loading and unloading cycles.
In accordance with one embodiment of the present invention, the apparatus is incorporated in an input/output section of a microelectronic workpiece processing tool. The input/output section receives the one or more cassettes by a workpiece cassette inventory assembly. The workpiece cassette inventory assembly can then selectively adjust the alignment of the one or more cassettes with respect to a corresponding workpiece staging assembly for transfer therebetween. The workpiece staging assembly receives the one or more cassettes from the workpiece cassette inventory assembly and positions them to allow access to individual workpiece positions of the one or more cassettes, including access to any microelectronic workpieces disposed at the workpiece positions.